Shorten build id

Build ids are limited to 64 chars, but now hit 66:

4.18.0-425.5.1.rt7.215.el8_7.mr3724_221110_1600.g211f.x86_64+debug

Reduce that to

4.18.0-425.5.1.rt7.215.el8_7.3724_123.g211f.x86_64+debug

This is formed from mr_id=3724 pipeline_id=123.

With these changes, the CKI part goes from 19 characters (.mr4567_9abcde_ghij) to currently 15 (.4567_703342232).

Fixes: https://gitlab.com/redhat/red-hat-ci-tools/kernel/cki-internal-pipelines/cki-internal-contributors/-/jobs/3305352417

Signed-off-by: Michael Hofmann mhofmann@redhat.com